Forming articles of multiple layers, whether the layers are of similar or different materials, is known. Layered rubber articles comprised of many alternating layers of different rubbers have been described by Frerking in U.S. Pat. No. 5,178,702, wherein air barrier/low temperature properties are improved in horizontally layered composites. Such composites can be prepared by hand by plying up alternating layers of two or more different rubber compounds.
Sluijters in U.S. Pat. No. 3,051,453 describes a mixing apparatus designed to mix two streams of liquid by splitting and rejoining the streams in a particular geometric way (a static mixer), which the instant inventors have found can be used with rubber to produce a layered, instead of a mixed product. Reilly et al. in U.S. Pat. No. 5,866,265 have used this concept to split elastomer streams and have caused the streams to flow back together to form a layered material. Said patent is incorporated herein by reference.
The apparatus and method taught by Reilly et al. comprised a single set of stacked dies and was useful for proving that the concept could be used to produce a layered material for laboratory characterization. No apparatus or method is known in the art for making commercially usable microlayered elastomeric materials.
All of the known methods and techniques are directly to forming linear, continuous products.